This invention relates generally to radiography, and more particularly to methods and systems for volumetric reconstruction using scattered X-ray radiography.
Radiography is sometimes used to generate volumetric, or three-dimensional, images of structures and systems when disassembly of the structures and systems is not desirable. For example, volumetric images may be used to service and repair aircraft, to detect foreign objects, and/or for reverse engineering purposes. Some known radiography systems use backscatter imaging to generate two-dimensional images that are a projection of a three-dimensional volume on an image plane. Such two-dimensional images cannot be used to generate three-dimensional images because the two-dimensional images lack depth information.
Some known systems for extracting depth information from backscatter images require collimation of a detector to limit return of the scattered X-rays from a specified depth. Detector collimation requires that the scan speed be reduced to collect enough scattered X-rays to produce an image with a sufficient signal to noise ratio. Also, because known systems are configured to penetrate to a particular depth, several scans have to be taken to produce an image with a significant depth of field. For example, imaging methods that include computed tomography generally rely on using geometry-processing algorithms to create a volumetric reconstruction from a series of two-dimensional transmission X-ray images. Transmission radiography is used to create a series of two-dimensional images from various perspectives about a central axis of an object, and relies on the assumption that photons will either pass through the object with zero scatter or be completely absorbed by the object. Because known computed tomography systems rely on transmission radiography, such systems require access to both sides (i.e., a front and a back side) of the subject object and therefore may be limited in use in some products, such as aircraft.
Accordingly, there is a need for radiography systems that enable volumetric reconstruction of objects without requiring access to both sides of the object. More particularly, there is a need for radiography systems capable of generating volumetric reconstructions of objects when only one side of the object is accessible.